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The commercial potential of composite polymer electrolytes (CPEs) is significant due to their ability to combine the advantages of both inorganic and polymer solid electrolytes. However, the unstable interface and insufficient ionic conductivity remain important challenges in practical applications of CPEs for achieving high-performance solid-state lithium batteries (SLBs). Herein, we construct a double-layer composite polymer electrolyte (D-CPE) by incorporating nanosized TiO 2 fillers with adjustable concentrations of oxygen vacancies into poly (ethylene oxide) (PEO)-based electrolyte composites. In the D-CPE structure, one CPE layer containing TiO 2 fillers with oxygen vacancies exclusively interfaces with the LiFePO 4 cathode, while the other CPE layer consisting of pristine TiO 2 fillers (with negatively charged surfaces) solely contacts the lithium anode. This design of D-CPE achieves high ionic conductivity, a broad electrochemical window, and interfacial stability without additional resistance at the electrolyte-electrolyte interface simultaneously. The LiFePO 4 /D-CPEs/Li battery exhibits excellent cycling stability at 0.1 C, maintaining a capacity of 157.2 mAh g−1 with a capacity retention rate of 99.1% after 100 cycles. Furthermore, even at 0 °C, it delivers an impressive discharge capacity of 133.1 mAh g−1 at 0.1 C. This work presents a simple and effective approach to achieving superior polymer-based electrolytes for high-performance solid-state lithium batteries. [ABSTRACT FROM AUTHOR]

Regenerable all-round Li–O 2 cathode featuring ultralong cycle life (up to 1423 cycles, 2846 h) and large areal capacity (over 20 mAh cm−2) at high rates (no less than 0.5 mA cm−2) is developed by integrating a series of complementary and comprehensive cathode material design and system engineering strategies. [Display omitted] Lithium–oxygen batteries promise ultrahigh energy density, yet one of the key barriers toward applications is the rapid performance decay during cycling especially at high rates, owing to the sluggish redox kinetics and severe parasitic reactions under elevated overpotentials within the cathode. In face of the above challenge, here we present a carbon nanotube sponge-based high-performance lithium–oxygen cathode by a series of approaches such as tailoring discharge product morphology to lower the overpotential, controlled sponge-compression for high mass loading to facilitate high-rate cycling, gradient electrolyte-immersion to rationally utilize its interior for efficient multiphase transport, and water treating for regenerated use. These 4 methods target different aspects of the electrochemical behavior in a Li–O 2 cathode, thus constituting a complementary and integrated strategy to overcome the challenges in this field. As a result, we achieve simultaneously an ultralong cycle life (1423 cycles, 2846 h) at high rate (0.5 mA cm−2) under low overpotential (charging below 4.0 V throughout 1100 cycles), also with an areal capacity over 20 mAh cm−2 and extended 500 cycles after regeneration. Such an overall performance is much superior to recently developed 3D metal foam or carbon-based cathodes. Our designed sponge cathode represents a promising candidate for developing durable, high-energy and high-power metal–air battery systems, pushing forward their practical application. [ABSTRACT FROM AUTHOR]